1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more particularly, to an LCD that can maintain a uniform cell gap, and a method of fabricating the same.
2. Discussion of the Related Art
Recently, researches on flat panel displays such as liquid crystal displays (LCDs), electro luminescence devices (ELDs), plasma display panels (PDPs), vacuum fluorescent displays (VFDs) and the like are in active progress. Among such flat panel displays, LCDs have such advantages as low voltage operation, low power consumption, lightweight and slim profile, full color realization. Therefore, the LCDs are widely used for a display for watches and calculators, computer monitors, monitors with a television receiving function, television sets, and hand-held terminals.
Such an LCD includes an array substrate having pixel electrodes formed thereon, a color filter substrate having a color filter layer and a common electrode formed thereon, and a liquid crystal layer interposed between the array substrate and the color filter substrate. An electric field is generated between the pixel electrodes and the common electrode, as a voltage is applied to the pixel electrodes and the common electrode. Liquid crystal molecules of the liquid crystal layer are aligned by the generated electric field to adjust light transmittance. By the adjustment of the light transmittance, light is converted into visible rays while passing through the color filter layer such that a desired image is displayed.
FIGS. 1A through 1C are sectional views illustrating a method for fabricating a color filter substrate according to a related art.
As shown in FIG. 1A, an opaque metal film such as chromium (Cr) having a low reflectivity is deposited on a transparent glass substrate 10 and is then patterned to form a black matrix layer 1. Alternatively, the black matrix layer 1 may be formed by coating a photosensitive black resin on the transparent glass substrate 10 and then exposing and etching the photosensitive black resin.
After the black matrix layer 1 is formed, a color filter layer including red, green and blue color filters 3, 5 and 7 is formed on the substrate 10 including the black matrix layer 1, as shown in FIG. 1B. The color filter layer is generally formed by a pigment dispersion method. In the pigment dispersion method, a photosensitive resist mixed with a prepared pigment is spin-coated, and the coated photosensitive resist is repeatedly exposed and developed to form the red color filter 3, the green color filter 5 and the blue color filter 7. For example, after a red photosensitive resist is spin-coated on the glass substrate 10, the coated red photosensitive resist is exposed and developed to form the red color filter 3. Next, a green photosensitive resist is spin-coated on the glass substrate 10, and the coated red photosensitive resist is exposed and developed to form the green color filter 5. Thereafter, a blue photosensitive resist is spin-coated on the glass substrate 10, and the coated red photosensitive resist is exposed and developed to form the blue color filter 7. By repeating the above steps, the color filter layer including the red color filter 3, the green color filter 5 and the blue color filter 7 is formed on the entire surface of the glass substrate 10.
After the color filter layer including the red color filter 3, the green color filter 5 and the blue color filter 7 is formed, a transparent resin having an insulating property is coated on the glass substrate 10 including the black matrix layer 1 and the color filter layer to form an overcoat layer 9, thereby planarizing the black matrix layer 1 and the color filter layer, as shown in FIG. 1C. After that, although not shown in FIG. 1C, a common electrode for applying a common voltage is formed on the overcoat layer 9.
FIG. 2 is a schematic plan view of a color filter substrate for a multi-model on glass (MMG) model.
The MMG model includes a plurality of panels having different resolutions on a single glass substrate. As one example of the MMG model, a VGA panel and an XGA panel are provided on a glass substrate, as shown in FIG. 2. A black matrix layer structure and a thickness of a color filter layer in the XGA panel are different from those in the VGA panel. Also, because the VGA panel has a pixel size larger than the XGA panel, the resolution of the VGA panel is lower than that of the XGA panel. Thus, because the MMG model LCD is provided with two panels having different resolutions together on a single glass substrate, it has an advantage of maximizing use efficiency of the glass substrate.
In the MMG model LCD, the color filter layer is, however, formed by a spin-coating method. Accordingly, an interval between the lattices of the black matrix layer of the XGA panel becomes different from that of the VGA panel. The difference in the intervals of the lattices between the XGA panel and the VGA panel raises a problem in that the thicknesses of the color filters formed between the lattices of the black matrix layer are different.
FIG. 3 is a schematic view illustrating a non-uniform cell gap between a XGA panel and a VGA panel in a MMG model LCD.
As shown in FIG. 3, the MMG model LCD is provided with panels having different resolutions. For this purpose, a color resist is coated on each of the panels by a spin coating method. When the color resist is spin-coated, the color resist spreads on a black matrix layer. As aforementioned, the intervals between the lattices of the black matrix layers formed on the panels having different resolutions are different. The different intervals cause the coated color resist to spread at a different spreading rate, so that the thicknesses of the color filters formed varies depending on the location. In other words, the thicknesses of the color filters of the XGA panel is greater than that of the color filters of the VGA panel. This indicates that the thickness of the color filter substrate of the XGA panel is greater than that of the color filter substrate of the VGA panel. Because of the difference in the thicknesses of the color filters of each of the panels having a different resolution, the cell gaps of the VGA panel and the XGA panel in the MMG model LCD is not uniform, as illustrated in FIG. 3.
To solve the above problem, it is suggested to disperse ball spacers when the array substrate and the color filter substrate are attached to each other or to arrange column spacers at a non-transmission region of the array substrate. However, these methods do not solve the above problem satisfactorily. The non-uniform cell gap causes a difference in optical path, so that picture quality deteriorates.